The NAS Security anti-virus service can scan files on a scheduled basis and can even scan files in real-time, protecting the data on the TeraStation from the threat of virus. The subscription service lasts for 1, 3 or 5 years from the date it is first used, and is provided as a unique serial number which is activated in the TeraStation web-based user interface. During an active subscription period, the service will continue to operate and receive automatic virus subscription updates from Trend Micro. Upon expiration of the service, the TeraStation will continue to operate, but the virus scanning features will stop working until a new subscription is applied. Once applied, virus subscription services cannot be transferred from one TeraStation to another.